export const blobToDataURL2 = (blob, cb) => {
  const reader = new FileReader()
  reader.onload = function(evt) {
    const base64 = evt.target.result
    cb(base64)
  }
  reader.readAsDataURL(blob)
}
export function blobToDataURL(blob, callback) {
  const a = new FileReader()
  a.onload = function(e) { callback(e.target.result) }
  a.readAsDataURL(blob)
}
